A hex socket fastener is a type of fastener with a threaded cylindrical barrel that mates with a complementary thread in a fixture. The threads of a hex socket bolt may mate with the internal threads of a complementary nut to hold a stack of parts together. Likewise, a hex socket head cap screw has a threaded cylindrical barrel that mates with the complementary threads in a fixture. The bolt and nut, or the screw and fixture, are kept together by a combination of thread friction and compression of the parts.
Hex socket screws and bolts are commonly known as ALLEN® screws and bolts, wherein ALLEN® is a U.S. trademark registered by Apex Brands, Inc., a Delaware corporation. Hex socket screws are threaded on one side of a cylindrical screw for threading onto a complementary thread in a fixture or a nut. The opposite end of the screw is the head which has a smooth or knurled exterior surface and a hexagonal socket. Similarly, hex socket bolts have a cylindrical body with one end having threading for mating with a complementary nut, and the other end having a hexagonal socket. Hex socket screws and bolts are used when hexagonal or square screws or bolts will not fit; however, the interior corners or surfaces of the socket are vulnerable to being rounded off.
Hex socket screws and bolts are traditionally removed using hand wrenches, commonly known as ALLEN® wrenches, by applying force to one or more internal side faces or corners of the socket to cause it's rotation. However, where the internal side faces or corners of the socket have been stripped or damaged, or where the fastener has been corroded, it is very difficult and time consuming to remove such screws and bolts.
A further complication of screw and bolt removal using manual tools is that where the screw or bolt is very large, such as those used in oil production, manual removal using an ALLEN® wrench of such damaged screws and bolts presents danger to the operator, or manual removal is impossible because of the degree of torque required for removal.
One type of device accomplishes fastener removal by sawing off the fastener, or by using a blow torch to cut the fastener out of a fixture. However, these methods of removal result in damage to the screw or bolt, or the fixture. This problem may be solved with devices which either drill into the screw, or cut into the screw, so that torque can be applied to the screw for removal. However, these devices also result in further stripping and rounding of the screw, and the process of drilling a hole and subsequent removal is time-consuming.
Devices for the removal of hex socket fasteners using an air impact tool exist; however, in one such device, a cartridge having many small parts is used to apply torque to the damaged screw or bolt. These multiple small parts of the cartridge, such as multiple helical springs, studs and screws holding gripping jaws together are prone to breakage.
A further complication is that cartridges and other parts of removal tools are held within a cylindrical housing a retaining ring or clip. The retaining ring or clip is prone to breakage, resulting in a damaged and useless tool.
Another complication of fastener removal using a hand-powered tool is side loading, or the mechanical binding of threaded surfaces against each other. When side loading occurs, heat builds up due to friction between the threaded surfaces, creating a gall which is carried through the housing, tearing out the threads, and actually impeding removal.
Yet another complication is “chattering”, where the tool does not perfectly conform to the size of the fastener. When rotative force is applied using an air impact tool, the removing tool “chatters” over the damaged corners of the fastener, further stripping the fastener, or damaging the tool interface with the fastener, causing ‘radii’ to form on the end of the tool.
A further problem is presented with a single device for fastener removal, because the device is limited in the size of fastener which can be removed with a single tool; that is, different sized fasteners cannot be removed with the same tool because the fastener heads cannot fit within the tool.
The use of a set of tools having a multiplicity of sizes to conform to different screw head sizes could solve the problem of imperfect conformance between the removal tool and fastener size. However, regardless of the size, the result is chattering from an imperfect size conformance; thus, stripping of the fastener socket occurs.
Further, the use of a set of tools having a multiplicity of sizes to conform to socket sizes presents another complication. If there exists a multiplicity of removal tool sizes in a set, the loss of one of the tools results in a useless tool set.
While the use of an air impact tool may eliminate much of the operator danger associated with hand wrenches, the use of an air impact tool presents a further problem. That is, the air impact tool itself creates a shock upon impact with the screw. When using sockets attached to air impact tools for screw removal, this shock impact can damage both the screw and adjacent surfaces. A further complication of some devices is that ridged teeth on the gripping surface of the jaws strip the screw socket.
It would thus be desirable to have a hex socket fastener removal tool that conforms to the size and shape of a multiplicity of sockets, where the jaws of the tool comprise one piece, rather than a multiplicity of smaller pieces which can be easily lost or damaged, and where the jaws are retained within a housing through a shock-absorbing canted coil spring.